Brettus

iTrader: (2)

I have cranked it right up and ended up with 7 PSI . It also restricts the opening of the wastegate quite a lot - it opens less than 1/2 way . I would imagine that it would make this spike problem worse although i did not experience it .

chris_rx8

You think I should have this problem with a stock ms exhaust and stock midpipe/cat.

mehidi@mail.com

i dynoed my car last night for the first time after putting a stock greddy kit on a completely stock car (stock exhaust, stock cat). custom cai, first run 3rd gear 4k rpm 10psi, 5.5k-9k rpm 5 psi. i though it was the boot gauge. set a second gauge right after the turbo, and one from the vac like off of the manifold. second run, 4.5k rpm first gauge reads 12psi second reads 10 psi, 6k rpm-9k rpm first reads 7 second reads 5psi. stock wastegate spring. using a interceptor x for now. will upgrade to an ap see what that does. but the shop i was at is saying (they usually work with rx7s) it could be the piggy back with the stock cat and the turbo waste gate valve is not designed well on the t618z. i was shown 2 different eclipse turbos that r the same size but different location and size for the valve. they said one of them does the same thing as the t618z and the other do not spike like that. they also said messing with the actuator shaft does help but it is not a solution. i am going to get a cat delete pipe, cobb ap and get a different spring (softer) so it will open earlier and use a boost controller. oh and the spikes got a little better when i adjuster the bov spring (harder setting).


at the end of it all that was that shops opinnion. what really is going on only greddy can tell.

Brettus

iTrader: (2)

what do you mean boost spike ?- You don't have a spike . What you are experiencing is just poor wastegate control and no boost controller is going to fix it.
A softer spring will make your control even worse .

mehidi@mail.com

no i wanted a softer spring to it opens earlier or attempts to like a 5 punder, i realized the one i have is a 7 from the previous owner. either way, after messing with the fuel a little bit the spikes are not that bad, i get 10-10.5 at 4-4.5k rpms at 3rd and 4th gear only now. softer spring with a good boost control worked for me on my integra that had a 16g turbo. wtb brettus, when u first put ur kit on did u have the upgraded turbo or u put that on later? i just wanted to get the characteristics of the greddy upgraded turbo. this t618z that comes stock of wak.

Brettus

iTrader: (2)

Can you explain a little more like what is your boost at the following rpm 3,3.5,4,4.5,5,5.5,6and6.5 . Still don't get what you mean by spike .


yes mine was always the upgraded so have not experienced what the stock Greddy is like .

mehidi@mail.com

ya this is what i see, first with all stock components, intx base map.
1st gear: 2.5-4k rpm 1-2 psi
4.5-7k 4-5 psi
2nd gear: 2.5k rpm 1-2 psi
3k-4k 3-5psi
4.5k-5.5k 5-6psi
6k- redline 5.5-6 psi
3rd gear : 2.5k rpm 1-2 psi
3k-4k 5-6psi
4.5k-5.5k 10psi
6k- redline 5.5-6 psi
4th gear: 2.5k rpm 1-2 psi
3k-4k rpm 5-6psi
4.5k-5.5k rpm 10psi
6k rpm - redline 5.5-6 psi

and yesterday i got 4th gear 4-6k rpm 10 psi and then it dropped to 6 psi after 6.5k rpm. but the first day was worse on every gear around 3-6rpm i got 10 psi. after a little playing with the bov and intx to lower the fuel it i got the above results. also my battery started to dye over night. discovered that the intx was keeping the fan on even after i removed the key from ignition. getting the cobb on tuesday. so brettus, do u get a linear boost? at what rpm does ur turbo spool to 5 psi on 3rd gear? how much did ur upgrade cost?

Brettus

iTrader: (2)

Thanks for that . I wouldn't describe what you are seeing so much as a spike - more a surge . Are you running a boost controller ?
If you are then it is not adjusted properly for low end spool up .
If not :
I would take the actuator rod off and check that the wastegate is not jammed in one position - that is what it seems like to me . Bad if it is jammed completely closed (it wont be) but not such a big deal if it is jammed slightly open (I actually do that on purpose on my setup) .

My boost is pretty linear from 3500 onwards (10psi) then starts dropping away at around 6500 down to about 7.5-8psi . This dropoff is perfectly normal and no amount of tweaking will get you 10psi to the redline on a stock Greddy. If you could do that we would see a whole lot of 320whp greddy 8s around - we dont.
The 60-1 upgrade from BNR costs about $1000 but my setup (the most whp anyone has made with greddy housings) has a 57 trim wheel which is close to the 50 trim wheel also offered by BNR . I would go for that one.

mehidi@mail.com

ya thats where i am going to start (actuator check) but that spike (surge) is getting better and bettter. i have relocated the vacuum source for the actuator and now i surge to 8-7 psi. does anyone make a gt28rs for this kit? i know the 3071 by mm but they want 2 grand for it. i was thinking of getting a ball bearing (small) for the greddy, just enough to do 300 whp. but as far as spiking is concerned i have settled on few things
1) the shop i took the car to doesn't know ****
2) fuel trim at low end plays a role is spikes and surges (i changed some of the trims and it got better)
3) stock greddy t618z is garbage compared to our expectations of it and its waste gate seems to be the cause of most engine blows (not saying all). i am the 5th 8 i know with this same problems and my other friends are using emanage which is base maped for maybe 7psi so spiking or surging is not exceptable. an upgraded turbo is a must if want ur car to last
4) vacuum source needs to be as close to the turbo as possible as i figured from the two gauge experiment.
5) listen to every thing brettus and jeff of mm says on their write up about the greddy kit. and for those of us who r trusting other people to do the work for us... don't. do ur own research and look over their work.

MazdaManiac

iTrader: (3)

Just a raw GT28 is gonna set you back almost a grand. By the time you pay a fabricator to built the adaptation parts, you will be close to $3k.
Never mind that the 28 is way too small - even "smaller" than the GReddy (which is a TD06-18g).

mehidi@mail.com

mazdamaniac, what is your opinion on this troubling spike/surge the greddy tubo has. do u think the ap tuning by mm can handle things like that or should i not get my wife her weekly pedicure and manicure + lingerie $$ and put it in a Garrett turbo?

Brettus

iTrader: (2)

No amount of tuning can correct a mechanical issue .

mehidi@mail.com

ok got it fixed. the turbo's oiling system was flushed, a vacuum nipple was added to the charge pipe before the the inter cooler for the waste gate actuator, and installed ap baseline which brought my afr to 14-13 at idle and 11-12-13 to boost and i do not go above 6 psi at any time

Brettus

iTrader: (2)

where was the line to the WG actuator coming from previous to this ?

mehidi@mail.com

2 different sources. i tried a vac on the intake manifold right above the ports, and i tried the vac source right after the TB. that was very stupid on my part. after reading jeffs thread i changed it to 2" from the turbo. i'm gonna try the old sources to see if it was the source, or the turbo cleaning or something else that fixed it.

Brettus

iTrader: (2)

correct

Are you sure your boost surge was at WOT and not part throttle ? Where were you measuring boost ?

Have a read of this thread and see if any of it rings a bell ..... I'm wondering if this so called "boost spike" issue that so many greddy users seem to suffer from is all related to actuator vac line source and boost controller hookup .
https://www.rx8club.com/series-i-major-horsepower-upgrades-93/where-did-you-plumb-your-boost-controller-into-uim-no-good-169316/

mehidi@mail.com

yes, partially. my situation is a little bit different. along with incorrect plumbing of vac source, i think my turbo might have had a mechanical issue. most users that use a brand new turbo kit do not have this issue. i bought my kit off of a blown motor. the turbo exhaust housing, turbine,and waste gate might have been affected. i know from my previous cars (turbo) that even with a external waste gate and a ball bearing turbo it is possible to get boost spike when u run very rich. also i have had internal waste gates that have no spikes what so ever even with rich conditions, ebay parts, bad oil conditions etc. i think it was a combo of all the factors especially turbo vac source. i am not using any boost controller btw.

oh and i got the surges mostly on wot

Brettus

iTrader: (2)

Again where were you measuring boost ? Post throttle body or pre throttle body ?

Here are the most likely causes of your issue:

*very low pressure reaching the WG actuator
*Mechanical binding - ie WG arm stuck in one position .

To get low pressure to the actuator (if you were seeing 10psi post throttle body ) you would have to have had a kink in your vac line or possibly a leak .

mehidi@mail.com

as i stated before on my first post i measured vac in 2 different places. one at the manifold and one before. but from my experience boots should never be measured before the intake manifold. it should always be the same source as ur ecu in this case int-x. my problem was boost source for the waste gate and i was running really really rich.

Brettus

iTrader: (2)

yeah kinda true . Measuring it before the throttle does give you some very useful information . For normal day to day operation , after the throttle is the "right" place to measure .


Don't see how running rich would have caused this but the source for the WG actuator could have an effect. At WOT it should not have made as much difference as what you saw . A leak or kinked hose is the more likely scenario .